Cellular Respiration and Fermentation

How do we harvest energy from food? There are two important ways a cell can harvest energy from food: fermentation cellular respiration

Start with Glycolysis Both start with the same first step: the process of glycolysis which is the breakdown or splitting of glucose (6 carbons) into two 3-carbon molecules called pyruvic acid. the process of glycolysis which is the breakdown or splitting of glucose (6 carbons) into two 3-carbon molecules called pyruvic acid. The energy from other sugars, such as fructose, is also harvested using this process. The energy from other sugars, such as fructose, is also harvested using this process. Glycolysis is probably the oldest known way of producing ATP. Glycolysis is probably the oldest known way of producing ATP.

Glycolysis: Glucose to Pyruvic Acid

And TWO ATP Molecules = Energy Actually 4 ATP molecules are created, but two are used up in the process.

Glycolysis is older than Oxygen

Facts about Glycolysis Glycolysis does NOT NEED OXYGEN as part of any of its chemical reactions. It serves as a first step in a variety of both aerobic and anaerobic energy-harvesting reactions. Aerobic Respiration = requires oxygen to produce ATP energy Anaerobic Respiration = energy is produced in the absence of oxygen Glycolysis happens in the cytoplasm of cells, not in some specialized organelle. Glycolysis is the one metabolic pathway found in all living organisms.

Fermentation In fermentation these pyruvic acid molecules from glycolysis are turned into some “waste” product, and a little bit of energy is produced. Out of many possible types of fermentation processes, two of the most common types are: lactic acid fermentation and alcohol fermentation

Lactic Acid or Ethanol & CO 2

Lactic Acid Fermentation Lactic acid fermentation is done by some fungi, some bacteria like the Lactobacillus acidophilus, in yogurt, and sometimes by our muscles. The 3-carbon pyruvic acid molecules are turned into lactic acid The 3-carbon pyruvic acid molecules are turned into lactic acid

Lactic Acid Fermentation Normally our muscles do cellular respiration like the rest of our bodies, using the oxygen supplied by our lungs and blood. However…. Under great exertion, when the oxygen isn’t supplied fast enough to keep up with the muscles’ need, our muscles can switch over and perform lactic acid fermentation.

Lactic Acid Fermentation When our muscles form lactic acid we develop that “morning after” effect where our muscles are very sore. Our over-exerted muscles feel stiff and sore even if they haven’t been physically injured because it takes the body some time to gradually wash away the lactic acid that built up. The excess lactic acid is carried away by our blood stream to our liver, which gets rid of it.

Yogurt It is the presence of lactic acid in yogurt that gives it its sour taste It is the presence of lactic acid in yogurt that gives it its sour taste

Korean Kimchi Kimchi can be traced back to ancient times. References to kimchi can be found as early as 2600–3000 years ago. Early kimchi was made of cabbage and beef stock only, and in the twelfth century people began to include other spices to create different flavors, such as sweet and sour flavors, and colors such as white and orange. In modern times however, the main spice and source of 'heat' for most Kimchi is a paste made from red chili peppers, a New World vegetable that was not available to Koreans until after 1500.

Alcohol Fermentation Alcohol fermentation is done by yeast and some kinds of bacteria. The “waste” products of this process are ethanol and carbon dioxide.

Beer, Wine, and Bread In bread making, it is the CO 2 which forms and is trapped between the gluten (a long protein in wheat) molecules that causes the bread to rise, and the ethanol evaporating that gives it its wonderful smell while baking. In bread making, it is the CO 2 which forms and is trapped between the gluten (a long protein in wheat) molecules that causes the bread to rise, and the ethanol evaporating that gives it its wonderful smell while baking.

Cellular Respiration In contrast to fermentation, in the process of cellular respiration, the pyruvic acid molecules are broken down completely to CO 2 and more energy released. C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Plus Energy (net of 36 ATP molecules)

Cellular Respiration There are three process steps in Cellular Respiration Glycolysis The Kreb Cycle Electron Transport Chain The Kreb Cycle and the Electron Transport Chain occur in the Mitochondria of the cell.

Cellular Respiration Steps

In a nutshell…Cell Respiration When your cells burn sugar fuel from your meal there are three parts to the job and you get some ATP. First you do glycolysis. Split that sugar right in half, and you make two ATPs: store some energy. Second comes the Kreb Cycle. Break it down to CO2 in your mitochondria, and you make more ATP. Third, your mitochondria transport those electrons. Grab their energy to make lots and lots of ATP. Then you dump those electrons and some extra hydrogen. Bond them onto oxygen and you get some water. Forty total ATPs: Glycolysis uses two, and eukaryotes (like you and me) use two more so the total’s 36 ATPs.